... ~16.0mm Standards: ASTM, BS, DIN, GB, JIS used mattress spring tempered spring steel wire Grade:55CrSi,60Si2Mn,65Mn ... 3. Quality assurance: Eddy current test online4.Service life: Ultra fine martensitic structure which could improve the fatigue life of ... spring5. Applicable Industriesl: Widely used in automobile, elevator, motorcycle, electric switches, high-speed rail, ...